In December 2020, the Hayabusa2 spacecraft returned the samples from the carbonaceous asteroid Ryugu to Earth. The first sample analysis from a NASA and international team reveals that asteroid Ryugu has a rich amount of organic molecules.

All known terrestrial life forms are composed of organic molecules, a wide variety of compounds formed from carbon combined with hydrogen, oxygen, nitrogen, sulfur and other elements. The idea that chemical processes in asteroids can create some of the components of life is supported by the fact that organic molecules can also be produced by chemical processes that do not involve life.

Many different types of amino acids were among the prebiotic organics detected in the sample. Prebiotic chemistry studies the substances and processes that may have led to life. Earthly life often uses specific amino acids as building blocks for proteins.

Proteins are necessary for life because they are used to make enzymes that speed up or control chemical reactions and to create structures of all sizes, including hair and muscles. The sample also contains a variety of organic molecules that form when liquid water is present, such as aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, and heterocyclic compounds containing nitrogen.

Hiroshi Naraoka of Kyushu University, Fukuoka, Japan, said: “The presence of prebiotic molecules on the asteroid’s surface, despite the harsh environment caused by solar heat and ultraviolet radiation, as well as cosmic rays under high vacuum conditions, suggests that Ryugu’s upper surface grains have the potential to protect organic molecules.” .”

“These molecules could be transported throughout the solar system and potentially disperse as interplanetary dust grains after being ejected from the asteroid’s upper layer by impacts or other causes.”

Solvent extractions from the Ryugu
Solvent extractions of the Ryugu samples on a clean bench (ISO6, class 100) in a clean room (ISO5, class 1000) performed by Hiroshi Naraoka at Kyushu University in Japan. Credits: JAXA

Jason Dworkin of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said: “So far, Ryugu’s amino acid results are largely consistent with what has been seen in certain carbon-rich (carbonaceous) meteorites exposed to the most water in space.”

Daniel Glavin of NASA Goddard, a paper co-author, said: However, sugars and nucleobases (components of DNA and RNA), which have been discovered in some carbon-rich meteorites, have not yet been identified in samples returned from Ryugu. It is possible that these compounds are present in asteroid Ryugu, but that they are among our analytical detection limits, given the relatively small sample mass available for study.

Dworkin said, “This work is the first organic analysis of the Ryugu sample, which will be studied for years to come. We’ll make a direct comparison between the samples from Ryugu and the sample from asteroid Bennu when NASA’s OSIRIS-REx mission returns it to Earth in 2023. OSIRIS-REx is expected to return much more sample mass from Bennu and will provide another important opportunity to search for traces of organic building blocks of life in a carbon-rich asteroid.”

Magazine reference:

  1. Hiroshi Naraoka et al. Soluble organic molecules in samples from the carbonaceous asteroid (162173) Ryugu. Science. DOI: 10.1126/science.abn9033